Method of forming an orthodontic brace

ABSTRACT

A model of the teeth in a patient&#39;s mouth and a prescription of desired positionings of such teeth are provided by the patient&#39;s orthodontist. The contour of the teeth in the patient&#39;s mouth is determined, preferably digitally, from the model. Calculations, preferably digital, on the contour and the desired positionings of the patient&#39;s teeth are then made to determine the geometry (e.g. grooves) to be provided in brackets for receiving an arch wire to form an orthodontic brace. Such geometry is intended to provide for the disposition of the arched wire on the brackets in a progressive curvature in a horizontal plane and a substantially linear configuration in a vertical plane. The geometry of the brackets is altered (e.g. by cutting grooves in the brackets at individual positions and angles and with particular depths) in accordance with such calculations of the bracket geometry. The brackets may be disposed on the model of the patient&#39;s teeth at positions dependent upon such calculations. A mold may be formed of the model of the patient&#39;s teeth and the brackets on such teeth. The model and the mold may be shipped to the orthodontist with written instructions for the disposition of the brace on the patient&#39;s teeth. Alternatively, an information sheet may be prepared, after the calculation of the bracket geometry, to specify the placement of the brackets on the patient&#39;s teeth and the disposition of the arch wire on such brackets. The brackets and the information sheet are sent to the orthodontist.

This application is a continuation of application Ser. No. 07/895,663,filed Apr. 29, 1992, abandoned which is a continuation of applicationSer. No. 07/467,162, filed Jan. 19, 1990, U.S. Pat. No. 5,139,419.

This invention relates to a method of forming an orthodontic brace froma plurality of brackets and an unbent arch wire such that the properforces are applied by the brace to a patient's teeth to move thepatient's teeth into a desired configuration. The invention also relatesto an orthodontic brace with such properties.

When the teeth in a patient's mouth are displaced from an even oruniform disposition, such displacements tend to produce problems over anextended period of time. For example, such displacements may produceproblems in the patient's gums. These problems may cause the retentionof teeth by the patient's gums to become weakened so that the teethbecome loose in the patient's mouth. The problem may become soaggravated that the teeth may eventually have to be removed from thepatient's mouth.

To prevent the conditions in a patient's mouth from deteriorating,dentists often attempt to reset the positions of the teeth in thepatient's mouth. The dentists do this by attaching braces to thepatient's teeth and by gradually adjusting the forces applied by thebraces to the teeth. These forces act against the teeth in the patient'smouth to move the teeth gradually toward the positions desired by thedentist.

The braces are generally formed by brackets and an arch wire supportedin a groove in each of the brackets. Each bracket is adhered to anindividual tooth by a pad forming a part of the bracket. The arch wireextends between the brackets on adjacent teeth and applies a force tothe teeth to move the teeth toward the positions defined by thepatient's orthodontist. Until now, the grooves on the different bracketshave been substantially uniform. Because of this, the forces of the archwire on the teeth have had to be adjusted by bending or otherwisedistorting the wires.

The techniques discussed in the previous paragraph have had somebeneficial effect. However, they are expensive and imperfect. One reasonis that they require a considerable amount of work by the orthodontistto adjust progressively the forces applied against the teeth. Anotherreason is that the bending and distortion of the arch wire to adjust theforces on the different teeth have been largely on an empirical basisbased in large part upon the experience of the orthodontist. As will beappreciated, even an experienced orthodontist is not able to bend ortwist an arch wire precisely so that the proper force will be producedon the brackets attached to the individual teeth.

It has been appreciated in the art that it would be desirable toconstruct the brackets so that the arch wire is planar in an elevationalview and is progressively curved in a plan view even after attachment tothe brackets and after the disposition in the patient's mouth of thebrace formed by the brackets and the arch wire. For example, such abrace has been proposed in U.S. Pat. No. 3,477,128 issued to Lawrence F.Andrews on Nov. 11, 1969 and U.S. Pat. No. 3,660,900 issued to LawrenceF. Andrews on May 9, 1972. In spite of the fact that such a brace hasbeen proposed for such a long time and that considerable work has beenperformed on providing such a brace, no one has been able as yet toprovide such a brace.

The proposals made by Andrews are based upon measurements made in a fewskulls. They are not made on an individual basis for each patient.Furthermore, the proposals made by Andrews involve only a limited numberof parameters. These parameters are mostly confined to individualcharacteristics of the grooves in the brackets. As will be appreciated,the proposals made by Andrews are quite crude and would not besufficient to provide, for the unique parameters represented by theunique configuration and disposition of the teeth in a patient's mouth,a brace in which the arch wire is planar in an elevational view and isprogressively curved in a plan view.

The Andrews patents are now twenty (20) years (in one case), or almosttwenty (20) years (in the other case), old. In that period of time, noone has been able to advance the state of the art beyond the crude stateproposed by Andrews. This is true even though a considerable effort hasbeen made, and a significant amount of money has been expended, toadvance the state of the art.

This invention provides a method of providing a brace which meets thecriteria discussed in the previous paragraph. Specifically, inaccordance with the method of this invention, a brace is provided whichhas a progressive curvature in a plan view plane and a substantiallylinear configuration in an elevational view and which exerts the properforces on the teeth in a patient's mouth to move the teeth to a desiredconfiguration predetermined by the patient's orthodontist. By providingsuch a brace, the method of this invention causes adjustments in theforces applied by the brace on the teeth in a patient's mouth to beminimized.

In one embodiment of the invention, a model of the teeth in a patient'smouth and a prescription of desired positionings of such teeth areprovided by the patient's orthodontist. The contour of the teeth in thepatient's mouth is determined, preferably digitally, from the model.

Calculations, preferably digital, on the contour and the desiredpositionings of the patient's teeth are then made to determine thegeometry to be provided in brackets for receiving an arch wire to forman orthodontic brace. Such geometry is intended to provide for thedisposition of the arched wire on the brackets in a progressivecurvature in a plan view and a substantially linear configuration in anelevational view. The geometry of the brackets is altered in accordancewith such calculations of the bracket geometry.

The geometry of the brackets may be altered in a number of differentways to provide the desired results. For example, the length, depth,width and positioning of the groove in the bracket may be individual toeach bracket. Furthermore, if there are any rounded corners or curvedsurfaces to be provided in the grooves in each bracket, these are alsodetermined on an individual basis. The height of each bracket and theangle of inclination of such bracket may also be individuallydetermined. The width of each bracket and the curvature of the surfaceadhered on the bracket to the tooth may also be individually determined.

The brackets may be disposed on the model of the patient's teeth atpositions dependent upon such calculations. A mold may be formed of themodel of the patient's teeth and the brackets on such teeth. The modeland the mold may be shipped to the orthodontist with writteninstructions for the disposition of the brace on the patient's teeth.

Alternatively, an information sheet may be prepared, after thecalculation of the bracket geometry and the formation of the brackets,to specify the placement of the brackets on the patient's teeth and thedisposition of the arch wire on such brackets. The brackets and theinformation sheet are sent to the orthodontist. The orthodontist isable, on the basis of the information in the sheet, to dispose the archwire on the brackets to form the brace and to dispose the brace in thepatient's mouth with the arch wire in a progressively curved dispositionin a planar view and in a linear configuration in an elevational view.

In the drawings:

FIG. 1 is a schematic flow chart of one embodiment of a methodconstituting this invention for forming a brace including an arch wirewhich is progressively curved in a plan view and is substantially linearin an elevational view;

FIG. 2 is a schematic flow chart, in additional detail, of the methodshown in FIG. 1;

FIG. 3 is a schematic view of equipment which may be used to perform oneof the steps in the method shown in FIGS. 1 and 2;

FIG. 4 is a schematic view of a tooth and illustrates how the equipmentshown in FIG. 3 performs the step in the method shown in FIGS. 1 and 2;

FIG. 5 is a fragmentary schematic view of a brace formed from aplurality of brackets and an arch wire and schematically illustrates apair of brackets and a portion of the arch wire in the brace;

FIGS. 6(a) through 6(e) are side elevational views illustrating how anindividual bracket in the brace can be provided with different types ofgeometry in accordance with the method represented by the flow charts ofFIGS. 1 and 2;

FIG. 7(a) through 7(e) are top plan views further illustrating how anindividual bracket in the brace can be provided with different types ofgeometry, other than those shown in FIGS. 6(a) through 6(e), inaccordance with the methods represented by the flow charts of FIGS. 1and 2;

FIG. 8 is a side elevational view schematically illustrating a pluralityof teeth and the disposition on such teeth of a brace made in accordancewith the method of this invention;

FIG. 9 is a schematic plan view illustrating the disposition of thebrace on the teeth in the patient's mouth;

FIGS. 10(a)-10(g) are side elevational views of brackets with differentslot configurations;

FIGS. 11(a)-11(c) are front elevational views of brackets with differentangles of the slots in the brackets; and

FIG. 12 is a perspective view of a model of the positioning andconfiguration of the teeth in a patient's mouth before the teeth arereset to the positions predetermined by the patient's orthodontist.

The method of this invention provides an optimal formation of a bracegenerally indicated at 10 in FIGS. 8 and 9. The brace 10 includesbrackets generally indicated at 12 and an arch wire 14 supported by thebrackets. The arch wire 14 is disposed in an arched configuration havinga progressive curvature when viewed on a plan basis (FIG. 9) and havinga linear configuration when viewed on an elevational basis (FIG. 8). Inthis way, there are no discontinuities in the arch wire 14 when viewedeither on a planar or an elevational basis.

Each bracket 12 includes a pad 16 and a support member 18 (FIG. 6) . Thepads 16 and the support members 18 may be constructed in a mannerdisclosed and claimed in U.S. Pat. No. 4,068,399 issued to Frank R.Miller, Craig A. Andrieko and Kenneth R. Premo on Jan. 17, 1978, andU.S. Pat. No. 4,165,561 issued to Frank R. Miller, Craig A. Andreiko andKenneth R. Premo on Aug. 28, 1979. The pads 16 and the support members18 are made from a suitable material such as stainless steel. Stainlesssteel is desirable because it will not corrode in the patient's mouth.The pads 16 may preferably be in the form of a mesh.

Each of the pads 16 is bonded at one surface, as by an adhering glue 20,to the supporting member 16 and the other surface of the pad is bondedto one of the patient's teeth. Alternatively, the bracket may beconstructed with integral pad or bonding base. The support members 18are provided with grooves 24 in an outer surface 26 to receive the archwire 14. The grooves 24 are provided with, lengths, depths, and widths,and are angled, to receive the arch wire 14 such that the arch wireexerts forces on the patient's teeth to move the teeth to aconfiguration predetermined by the patient's orthodontist. The differentlengths and depths and angles the grooves 24 are schematically shown inFIGS. 10(a)-10(g). The different angles of the grooves 24 areschematically shown in FIGS. 11(a)-11(c).

To perform the method constituting this invention, a patient'sorthodontist provides a model 30 (FIG. 12) of the teeth in the patient'smouth as such teeth actually appear, from the standpoint of positioningand configuration, in the patient's mouth. This may be provided byhaving the patient bite into a plasticizable material to define a femalemold. This mold is then used to form the model. The orthodontist alsoprovides a prescription of a desired positioning and configuration ofthe teeth in the patient's mouth. The dentist supplies the mold and theprescription to a laboratory, which then performs the steps in themethod of this invention.

The laboratory first determines the contour of each of the teeth in themodel 30. This contour may constitute the thickness of the tooth atprogressive positions in the vertical direction between the tip of thetooth and the patient's gum. The contour of each tooth in the model 30may constitute a mesio-distal profile. This represents the thickness ofeach tooth at a median position between the opposite lateral ends of thetooth. Alternatively, additional contours may be determined for eachtooth in the model at positions displaced from the median position. Thecontours are preferably determined on a digital basis to facilitate theprocessing of this information with other information determined in thelaboratory.

FIG. 3 illustrates apparatus, generally indicated at 40, for determiningthe contour of each tooth in the model 30, one of these teeth beingillustrated schematically at 42 in FIG. 4. As shown in FIG. 3, theapparatus 30 includes a platform 44 for supporting the model 30 in amanner so that any selected tooth in the model 30 can rest on theplatform. A probe 46 is supported on a stanchion 48 for movement in thevertical direction. The probe 46 is accordingly movable downwardly inFIG. 3 to contact the tooth whose contour is being determined. This isindicated by an arrow 50 in FIG. 3. The platform 44 is movablehorizontally to probe the contour of this tooth at progressive positionson the tooth. This is indicated schematically by arrows 54 in FIG. 3.

It will be appreciated that the apparatus shown in FIG. 3 and describedin the previous paragraph constitutes only one type of apparatus whichmay be used to determine the contour of the patient's teeth. Forexample, apparatus employing lasers, sonic elements or elementsemploying machine vision may also be used to determine the contour ofthe patient's teeth.

The prescription of the desired positionings and configuration of thepatient's teeth are used to compute the geometry of the brackets. Thisinformation may relate to several different parameters. For example, theinformation may relate to various parameters defining the grooves 24 inthe support members 18. These parameters may include the angle of thegroove 24 in the support member 18, the lateral position of the groovein the outer surface 26, the width of the groove and the depth of thegroove. The geometry of the groove 24 may also involve other parameterssuch as curvatures in the groove or configurations, other than linear,in the walls of the grooves to provide the brackets with the desiredparameters.

The geometry of the brackets 12 may also involve other parameters suchas variations in the distance between the surfaces 20 and 26 on thesupport member 18 in an elevational view. This is schematically shown inFIG. 6(e). The minimum distance is shown in solid lines in FIG. 6(e) andthe maximum distance is shown in broken lines in FIG. 6(a). The geometryof the brackets 12 may also involve additional parameters such asvariations in the angle of the surface 20 relative to the surface 26 ofthe support member 18 on an elevational basis. Different angles of thesurface 20 relative to the survace 26 of the support member 24 areschematically illustrated in FIGS. 6(b) and 6(d) .

Other parameters involved in the geometry may be the width of eachsupport member 18 to have the width correspond substantially to thewidth of the teeth to which the bracket including such support member isto be bonded. Furthermore, indicated in FIG. 6(a) and by solid andbroken lines in FIG. 6(c), the pad 16 may be provided with a curvaturein an elevational view corresponding to the curvature of the tooth towhich the pad is to be bonded.

FIG. 7 indicates how particular parameters of the brackets 12 may bevaried in the plan view. For example, FIG. 7(a) indicates how thethickness of the bracket may be varied in the plan direction. FIGS. 7(b)and 7(c) indicate examples in a plan view of different angles in thebrackets 12. FIGS. 7(d) and 7(e) illustrate different curvatures of thebrackets 12 in a plan view.

FIGS. 10(a)-10(g) illustrate different configurations of the brackets inelevation. For example, FIGS. 10(a) and 10(b) illustrate differentdepths of the slot 24 in the bracket 12. FIGS. 10(c) and 10(d)illustrate a different height of the slot 24 than FIGS. 10(a) and 10(b)and further illustrate different depths of the slot for such differentheight. FIGS. 10(e)-10(g) illustrate different angles at which the slot24 can be disposed in the bracket 12. FIGS. 11(a)-11(c) are frontelevational views showing different angles of the slot 24 in the bracket12.

The different parameters are provided with characteristics to providethe arch wire 14 with a progressive curvature in a plan view and asubstantially linear configuration in an elevational view when the archwire 14 is attached to the support members 18. The computations alsoindicate how the brackets 12 should be disposed on the patient's teethfrom vertical, lateral and rotational standpoints.

It will be appreciated that the teeth in the patient's mouth may havesome rebound after the arch wire 14 and the brackets 12 have beenremoved from the patient's mouth. It may accordingly be desirable toprovide the arch wire 14 with a curvature representing some overshoot inthe positioning of the patient's teeth beyond the optimal positioning ofthe teeth in the patient's mouth. This is considered to be within thescope of the invention. As used in the claims, the term "desiredpositioning of the teeth in a patient's mouth" is intended to includesuch an overshoot if the curvature of the arch wire 14 is designed toprovide such an overshoot.

The computations discussed in the previous paragraph are then stored ina memory. The computations are also used to cut the grooves 24 in thesupport member 18 and to provide the support member and the pad 16 withthe preferred geometry discussed in the previous paragraphs. In oneembodiment of the method constituting this invention, the brackets aredisposed on the teeth in the model in accordance with such computationsand are adhered to the teeth on the model with a glue providing for arelatively easy removal of the brackets from the teeth. A female mold isthen made of the model with the brackets properly positioned on themodel.

The model with the brackets properly positioned on the teeth is thenshipped to the orthodontist. An information sheet indicating the properdisposition of the brackets 12 on the teeth in the patient's mouth isalso shipped to the orthodontist to instruct the orthodontist how todispose the brackets 12 on the patient's teeth and how to install thearch wire 14 on the brackets. A duplicate information sheet may beretained by the laboratory for future reference. The female mold mayalso be shipped to the orthodontist. This may provide the orthodontistwith an opportunity of making a female mold after the positioning of thebrackets 12 on the teeth and comparing this female mold with the moldshipped to the dentist by the laboratory.

Alternatively, a map may be prepared by the laboratory. This may showsthe proper disposition of the brackets on the teeth in the patient'smouth. The laboratory may ship this map, the brackets 12, the arch wire14 and the information sheet to the orthodontist.

The method of this invention offers certain advantages over the priorart. It provides for the formation of brackets with proper geometry toprovide for the disposition of the bracket properly on the teeth and thedisposition of the arch wire in the brackets such that the arch wire hasa progressive curvature in a plan view and a substantially linearconfiguration in an elevational view. Furthermore, the geometry of thebrackets is such that the arch wire exerts a force on the teeth in thepatient's mouth to move the teeth to a desired configuration prescribedby the orthodontist. The brackets are formed with the properconfiguration automatically and without human intervention.

The brace 10 of this invention also has certain important advantages. Itis formed on an individual basis for each patient to displace the teethin that patient's mouth to a configuration and positioning prescribed bythe patient's orthodontist. The brace 10 is formed on this individualbasis by determining through calculations the geometry to be providedfor the different brackets 12 in the brace. This geometry is such thatthe arch wire 14 has a progressive curvature in a plan view and asubstantially linear disposition in an elevational view even after thearch wire is attached to the brackets.

It will be appreciated that the method of this invention may be used toform a brace only for a limited number of successive teeth in apatient's mouth. For example, the method of this invention may be usedto form a brace only for the incisors or for the teeth between orincluding the bicuspids.

As will be appreciated, data processing systems are used in thisinvention to determine the contour of the teeth in the model on anindividual basis. Software capable of being used to provide thesecalculations is attached to this application as Exhibit A and isconsidered to be a part of the specification. Data processing apparatusis also used to determine the geometry of the brackets 12. Such dataprocessing processing equipment may include CAD/CAM systems nowcommercially available from a number of companies including DaisySystems, Sun Microsystems and Apollo Computer (now a part ofHewlett-Parkard Company).

Although this invention has been disclosed and illustrated withreference to particular embodiments, the principles involved aresusceptible for use in numerous other embodiments which will be apparentto persons skilled in the art. The invention is, therefore, to belimited only as indicated by the scope of the appended claims.

We claim:
 1. A method for determining orthodontic bracket geometrycomprising the steps of:generating records in a digital computercontaining digital tooth shape data containing informationrepresentative of shapes of the outer surfaces of individual teeth of apatient; producing in a digital computer records containing digitaltooth finish position data containing information representative ofdesired relative positions of the patient's teeth; producing records ina digital computer containing digital archwire configuration datadefining the shape of an orthodontic archwire; producing in a digitalcomputer records containing digital bracket position data establishing abracket placement position on the outer surface of each of a pluralityof the patient's teeth; calculating in a digital computer, for eachtooth of the plurality, based on the tooth finish position data and thebracket position data and on the archwire configuration data,configuration data of a bracket having a slot engageable with anarchwire and which, when each bracket is appropriately oriented andpositioned on the respective tooth at the bracket placement position andengaged at the slot with the archwire, will exert forces on the teeth tomove the teeth to desired relative finish positions whereat the archwireexerts minimal forces on the teeth; and generating a digital signalcontaining information for the fabrication of a bracket in accordancewith the calculated configuration data.
 2. A method of claim 1 furthercomprising the step of:driving an appliance fabricating machine inresponse to the appliance geometry data to manufacture an orthodonticappliance to connect to the teeth on the contours thereof and configuredto move the teeth of the patient to the desired relative positions. 3.The method of claim 1 wherein:the tooth finish position data is at leastin part calculated from prescription information provided by anorthodontist.
 4. The method of claim 1 wherein:the tooth positionalinformation calculating step includes the step of calculating relativefinish positions of the teeth at least in part from the tooth shapedata.
 5. The method of claim 1 wherein:the information representative ofthe shape of the teeth includes information of the thickness of thetooth at progressive positions; the tooth finish position data isrelated to the thickness information; and the information of tooththickness is the information on which the calculating step is, at leastin part, based.
 6. The method of claim 1 wherein:the bracketconfiguration calculating step includes the step of calculating theconfigurations of the brackets such that an archwire connected to eachbracket forms a progressive curvature in a plane when the patient'steeth are each in their respective finish positions.
 7. The method ofclaim 1 wherein:the tooth finish position data produced containsinformation of desired relative positions of tooth shape data withrespect to an orthodontic archwire.
 8. The method of claim 1 wherein:thetooth finish position data produced contains information of desiredrelative positions of tooth shape data of different teeth.
 9. The methodof claim 1 wherein:the records generating step includes the step ofgenerating digital tooth shape data containing informationrepresentative of a mesio-distal profile of each of a plurality of thepatient's teeth.
 10. The method of claim 1 wherein:the recordsgenerating step includes the step of deriving tooth shape dataindirectly from at least one model of the actual shapes of the patient'steeth.
 11. The method of claim 1 wherein:the records generating stepincludes the step of deriving, indirectly from at least one model of theactual shapes of the patient's teeth, tooth shape data containinginformation representative of a mesio-distal profile of each of aplurality of the patient's teeth.
 12. The method of claim 1 wherein:therecords generating step includes the step of scanning, with a mechanicalprobe, at least one model of the actual shapes of the patient's teethalong a line representative of a mesio-distal profile of each of aplurality of the patient's teeth.
 13. The method of claim 1 wherein:therecords generating step includes the step of scanning, with a mechanicalprobe the shapes of each of a plurality of the patient's teeth andgenerating tooth shape data thereby.
 14. The method of claim 1wherein:the records generating step includes the step of deriving,scanning, with a mechanical probe, the shapes of a plurality of thepatient's teeth along a line representative of a mesio-distal profile ofeach of a plurality of the patient's teeth.
 15. The method of claim 1wherein:the records generating step includes the step of scanning, witha mechanical probe, at least one model of the actual shapes of thepatient's teeth and generating tooth shape data thereby.
 16. A method ofdetermining orthodontic bracket geometry comprising the stepsof:generating digital tooth shape data containing informationrepresentative of shapes of the outer surfaces of individual teeth of apatient; producing digital tooth finish position data containinginformation representative of desired relative positions of thepatient's teeth; calculating, in a digital computer and based on thetooth finish position data and tooth shape data for each of a pluralityof the patient's teeth, configuration data of a bracket, theconfiguration data including digital numerical values representing adimension, position and inclination of a slot in the bracket that willengage an archwire so as to move the teeth to the desired relativepositions; and fabricating a bracket in accordance with the calculatedconfiguration data, including the steps of generating a control signalin accordance with the digital numerical values and cutting in thebracket a slot having the dimension, position and inclination of thecalculated configuration data.
 17. The method of claim 16 wherein:theconfiguration data calculating step includes the step of calculating, inthe programmed digital computer and based on the foregoing information,the configurations of brackets for attachment to teeth of the patient,the calculating step including calculating data of the position of aslot on the bracket, depth of the slot in the bracket and angle of theslot in the bracket, such that each slot is engageable with an archwire;and the fabricating step further comprises the step of cutting a slot ina bracket at the calculated depth, position and angle.